// Copyright 2004-2010 Castle Project - http://www.castleproject.org/
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//     http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

namespace NVelocity.Runtime.Parser
{
	using System;

	/// <summary> 
	/// This interface describes a character stream that maintains line and
	/// column number positions of the characters.  It also has the capability
	/// to backup the stream to some extent.  An implementation of this
	/// interface is used in the TokenManager implementation generated by
	/// JavaCCParser.
	///
	/// All the methods except backup can be implemented in any fashion. backup
	/// needs to be implemented correctly for the correct operation of the lexer.
	/// Rest of the methods are all used to get information like line number,
	/// column number and the String that constitutes a token and are not used
	/// by the lexer. Hence their implementation won't affect the generated lexer's
	/// operation.
	/// </summary>
	public interface ICharStream
	{
		/// <summary>
		/// The currenct character.
		/// </summary>
		char CurrentCharacter { get; }

		/// <summary> Returns the next character from the selected input.  The method
		/// of selecting the input is the responsibility of the class
		/// implementing this interface.  Can throw any java.io.IOException.
		/// </summary>
		bool ReadChar();

		/// <summary> Backs up the input stream by amount steps. Lexer calls this method if it
		/// had already read some characters, but could not use them to match a
		/// (longer) token. So, they will be used again as the prefix of the next
		/// token and it is the implemetation's responsibility to do this right.
		/// </summary>
		void Backup(int amount);

		/// <summary> Returns the next character that marks the beginning of the next token.
		/// All characters must remain in the buffer between two successive calls
		/// to this method to implement backup correctly.
		/// </summary>
		bool BeginToken();

		/// <summary> Returns a string made up of characters from the marked token beginning
		/// to the current buffer position. Implementations have the choice of returning
		/// anything that they want to. For example, for efficiency, one might decide
		/// to just return null, which is a valid implementation.
		/// </summary>
		String GetImage();

		/// <summary> 
		/// Returns an array of characters that make up the suffix of length 'len' for
		/// the currently matched token. This is used to build up the matched string
		/// for use in actions in the case of MORE. A simple and inefficient
		/// implementation of this is as follows :
		///
		/// {
		/// String t = GetImage();
		/// return t.substring(t.length() - len, t.length()).toCharArray();
		/// }
		/// </summary>
		char[] GetSuffix(int len);

		/// <summary> The lexer calls this function to indicate that it is done with the stream
		/// and hence implementations can free any resources held by this class.
		/// Again, the body of this function can be just empty and it will not
		/// affect the lexer's operation.
		/// </summary>
		void Done();

		/// <summary>
		/// Gets the column.
		/// </summary>
		/// <value>The column.</value>
		int Column { get; }

		/// <summary>
		/// Gets the line.
		/// </summary>
		/// <value>The line.</value>
		int Line { get; }

		/// <summary>
		/// Gets the end column.
		/// </summary>
		/// <value>The end column.</value>
		int EndColumn { get; }

		/// <summary>
		/// Gets the end line.
		/// </summary>
		/// <value>The end line.</value>
		int EndLine { get; }

		/// <summary>
		/// Gets the begin column.
		/// </summary>
		/// <value>The begin column.</value>
		int BeginColumn { get; }

		/// <summary>
		/// Gets the begin line.
		/// </summary>
		/// <value>The begin line.</value>
		int BeginLine { get; }
	}
}